1. Field of the Invention
The present invention generally relates to a compressor used for an air conditioner (an air conditioning machine) and more particularly to a compressor used for an air conditioner for a vehicle (a car air conditioner).
2. Description of the Related Art
It is necessary, for provision of comfort, to use an air conditioner to adjust the temperature, humidity, air flow and air cleanness inside a room. The adjustment of temperature and the like by an air conditioner are accomplished by a compressor in a refrigerator (or a heat pump) circulating a gas and the gas performing a refrigeration cycle (or a heat-pump cycle).
Recently, weight and size reduction are required for all machines and compressors are also preferably made light and compact. More particularly, in case of a refrigerator for a car, the requirement of weight reduction and compact size are high in view of an improvement of fuel consumption, an improvement in design flexibility.
To realize a further weight reduction, a compact size of a compressor, the new ideas which are not occupied by accepted ideas are required and the capability of various designs of the compressors is effective.
However, conventionally, in a swash plate compressor 400, as shown in FIG. 4, it has been considered a matter of course that a coil spring 432, forward biasing the rear end of a main shaft 416, should be disposed in a spring chamber 440 which is formed by a valve plate 414 and a shaft aperture 441 provided in shaft center portion of a cylinder block 412. Thus problems, in which the design flexibility of a cylinder block 412, a rear housing 413 etc. are restricted and the further weight reduction, compact size, of a compressor have been prevented because of the requirement to provide a suitable space for the spring chamber 440, have arisen.
Also, in a conventional wobble type compressor 500, as shown in FIG. 5, coned disc springs 532 forward biasing the rear end side of a main shaft 516 may be disposed in a spring chamber 540 which is formed by a valve plate 514 and a shaft aperture 541 provided in a shaft center portion of a cylinder block 512. However as a coned disc spring generally has a large spring constant so that a small deflection of the coned disc spring considerably varies the actuating force thereof, precise adjustment of the actuating force is difficult. For example, if the installation position is moved slightly by an accumulation of tolerances of elements, the force which biases a main shaft forward is varied considerably. Thus when a main shaft is designed to be stably retained by using coned disc springs, it unpreferably causes problems such as an increase of manufacturing cost of a compressor.
With these above-mentioned problems being taken into account, the present invention has been developed. The purpose of the present invention is to provide a compressor in which the main shaft thereof is biased forward by a coil spring, of which the design flexibility is increased and of which weight reduction, a compact size and the like can be facilitated.
The inventor of the present invention has studied in earnest to solve the above problems and, after trial and error, has found that a recess or a seat portion, which defines a portion of a spring chamber that accommodates a coil spring forward biasing a main shaft, can be disposed in a rear housing, so that the compressor of the present invention has been developed.
That is, in the compressor of the present invention, which comprises a main shaft that receives a driving force of a power source from front side and is rotated, a front housing which has a shaft aperture that rotatably supports the front side of said main shaft, a cylinder block which has a shaft aperture, that is located on the rear side of said front housing and rotatably supports the rear side of said main shaft, and cylinders that are disposed in parallel to said shaft aperture on the outer circumferential side of said shaft aperture, a rear housing which has a suction chamber and a discharge chamber that are disposed on the rear side of said cylinder block and can communicate with the inside of said cylinders, pistons which are reciprocatably inserted into said cylinders, a suction valve which is interposed between said cylinder block and said rear housing and only allows a gas to be drawn from said suction chamber into said cylinders, a discharge valve which is interposed between said cylinder block and said rear housing and only allows the gas to be discharged from the inside of said cylinders to said discharge chamber, a swash plate which oscillates in conjunction with the rotation of said main shaft and can reciprocate said pistons, and a coil spring which is disposed on rear side of said main shaft and biases said main shaft from rear side to front side, the rear housing including a recess or a seat portion which defines at least a part of a spring chamber that accommodates the coil spring.
At least a part of a spring chamber, which accommodates the coil spring biasing the main shaft, is defined by the recess or the seat portion which is located in the rear housing, so that the flexibility of locations in which the spring chamber is positioned increases and the design flexibility of the compressor is enlarged. Thus, for example, the weight reduction, compact size and the like of the compressor and, more concretely, such as a shortening of longitudinal length thereof, can be realized more easily.
In addition, as the coil spring biases the main shaft from rear side to front side, the biasing force can be adjusted easily and the biasing force does not vary considerably due to a small movement of the installation position of the coil spring or the like. Therefore the main shaft is surely retained and an increase in the manufacturing cost of a compressor and the like does not occur.
Also, preferably, the spring chamber in the compressor communicates with a crank chamber, which is defined by the front housing and the cylinder block, and the recess or the seat portion comprises a communication passage which communicates the spring chamber to the suction chamber.
In the compressor, the crank chamber communicates with the suction chamber so as to avoid a pressure increase in the crank chamber due to blow-by of gas or the like and the communication passage between the crank chamber and the suction chamber can be simplified by locating the communication passage thereof in the spring chamber and the recess or the seat portion which defines at least a part of the spring chamber.
Further the suction chamber is more preferably defined adjacent to the outer circumferential side of the recess or the seat portion.
Because the suction chamber is located adjacent to the outer circumferential side of the recess or the seat portion, the communication passage can be further shortened, the communication passage between the spring chamber and the suction chamber can be simplified and weight reduction, a compact size, an improvement in production efficiency, can be facilitated.
Moreover the recess can be shaped as, for example, a circular hole which comprises a seat surface, that supports the end surface of the coil spring, in the bottom thereof. The seat portion may be merely a plane contact surface and may also comprise an annular groove corresponding to the coil diameter of the coil spring.
Also the compressor may be either a swash plate compressor or a wobble type compressor and also either a valuable displacement type or a fixed displacement type may be acceptable. The compressor may be used not only for a refrigeration cycle but also for a heat pump cycle. Moreover the compressor may be used for general purposes as well as for vehicular purposes. The pistons thereof may be either single-headed or double-headed. The swash plate must be oscillatable but is not necessarily rotatable such as a swash plate (a rod plate) of a wobble type compressor.
The present invention may be more fully understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings.